Radioreceiver



P 15534- I F. GOTTSGHALK 1,972,139

' RADIORECEIVER Filed Sept. 2L7 1950 Fly 5.

INVENTOR Ey- BY g ATTORNEY Patented Sept. 4, 1934 RADIORECEIVER Fritz Gottschalk, Berlin, Germany, assignor, by

mesne assignments, to Radio Patents Corporation, New York, N'. Y., a corporation of New York Application September 17, 1930, Serial No. 482,424 In Germany September 25, 1929 8- Claims. (Cl; 25020) This invention refers to improvements in radio receivers and methods of operation thereof and more particularly to receivers which employ an intermediate frequency derived from the frequency of an incoming wave carrying a radio message. Such receivers are commonly known as super-heterodyne receivers and, in general, provide a local source for producing oscillations of different frequency from the frequency of the incoming oscillations carrying the radio message, both oscillations being superimposed upon each other to produce beats from which a corresponding intermediate frequency is derived, which may be amplified effectively by means of a selective amplifier, especially designed for such intermediate frequency.

The object of the present invention is to'provide a radio receiving circuit operating according to the super-heterodyne principle in particular for receiving short waves, which issimple in construction and easyin operation and which comprises an extended range of operating or receiving frequencies.

A more specific object of the. invention is to provide novel means, inconnection with a superheterodyne receiving system for short waves, whereby a local frequency, separate from the frequency of an incoming wave is available in a circuit with a frequency response characteristic broad enough for carrying currents of an incoming wave, in such a. manner that when. the circuit is properly tuned, a-local oscillation-is automatically coordinated to the receiving frequency, so as to yield a definite and predetermined intermediate frequency forwhich the receiver has been particularly designed.

Another object of the invention isto provide a super-heterodyne circuit, especially for receiving short electric waves, in which a single tuning operation is utilized for receiving an incoming wave and for producing a corresponding local oscillation to be superimposed upon the received oscillations.

These and further objects of the invention will become more apparent as the following detailed description proceeds, taken with reference tothe accompanying drawing, in which some embodiments of the invention have been illustrated. I

The description, as well as the drawing, is intended, however, to be illustrative only of the inventive principle, which, it is understood, is subject to many modifications, all comingwithin its broadand most comprehensive scope, as expressed in the appended claims.

Figure 1 illustrates a. number of resonance necessary. I

curves explanatory of the theoretical principle on which the invention is based.

Figure 2 illustrates a super-heterodyne receiving circuit, primarily intended for the reception ofshort waves in which the invention has been Q embodied.

Figure 3 is a similar circuit toFigure 2, with a slight modification.

Figure 4 showsa further modification of a circuit, according to Figures 2 and 3. I

Similar references refer tosimilar elements throughout the different views of the drawing.

As. pointed out, the invention is concerned primarily with receivers for short electric waves (below about 150 meters), utilizing the superheterodyne principle. In one type of such receivers, known as thetropadyne circuit, the receiving vacuum tube, arranged in feed back connection, serves, at the same time, as a local oscillator; Thus, both the local oscillation is applied 15 to the grid of the vacuum: tube through the feed back circuit connection with the anode circuit and, at the same time, the wavecarrying the message andreceived from an input or antenna system is also: applied to the grid ofthe tube. This makes it necessary to provide two circuits, one of which is tuned to the signal wave length received (for instance, 30.5 meters) and the other which has to be tunedto the wave lengthof local oscillation of, (for instance, 30 meters) differing 85.

from the signal wave length by a predetermined and fixed amount, equal to desired intermediate frequency for which the receiver has-been designed. In such a system it is also necessary to provide means for decoupling both the local, circuit and receiving circuit for preventing mutual interference..

In accordance with the present invention, a single circuit is used, which is connected with the input or antenna circuit and which serves to apply the receiving oscillations tothe grid of a receiving tube known as the mixer tube and to produce simultaneously a free local oscillation necessary forv the heterodyning action. In such an arrangement only one tuning means has to be attended to, instead of two different adjustments, as in the case of the older circuit referred to above. Furthermore ,no decoupling means and consequently further diflicultfadjustments .are

, The invention is based'on the recognition that,

especially within the range of short waves, the

resonance curve of thecommon input circuit coupled with the antenna circuit and tuned to the receiving wave length, when properly de- The operator of such a receiver need not make! any longer a distinction between the two' waves when operating the set, but has to adjust only a single turning condenser to W receive a desired station, in the same manner as in the case'of an ordinary receiver not using the heterodyne principle.

Referring more particularlytoFigure 1 :this shows two resonance curves, particularly referring to short waves. The maximum of all such curves has acertain width, whereby, for instance, resonance conditions prevail, not only'fortl ewave length of 30 meters '(see right hand curve), but

also for thefneighboring waves of 30.5 and 29.5

meters, respectively. One of these waves, for infrequency of about2000 meters, which frequency short wave super-heterodyne receivers. Referring "to the'left hand resonance curve for 20 meter resonance wave length, the waves 20.2 meters and 19.8 meters, forming the limiting side wave of the band of substantially constant; that is, resonance amplitude, are in similar relation to the resonance frequency. l

Thus, as a tube oscillating at awave length of, for instance, 30 meters, will also be excited at a wave length of 30.5 meters, equal tothe wave length of an incoming signal, whereby this wave is automatically coordinated to the local wave, in such a manner that by superimposition ofboth waves the required intermediate frequency of the receiver for which the intermediate frequency amplifier'is sharply selective, is generated without the necessity of a second circuit and the necessary additional adjustments." Naturally, other intermediate frequencies are produced by other frequencies coming within the scope of thereso- .nance curve. These intermediate frequencies,

however, will be filtered out by the intermediate frequency amplifier 11, which, as is well known according to the specified characteristics of the In case that the'width of the resonance curve should not be sufficient tocover the receiving frequency, as well as a desired side frequency necessary for producing a' required intermediate frequency, theresonance curve, as is understood, may be artificially broadened out. This may, for instance, be effected by properly designing the ratio of the capacity reactance to the inductive reactance of the circuit, as well as by proper design or its ohmic resistance, as by employing'any one of the known means in'the art 'to' produce what is known as band pass characteristic of a circuit. Referring tolT'igure 2, which illustrates one'embodiment of the invention, the'antenna isshown to be inductively coupled with the coil 5 of'theoscillatory circuit, which, furthermoracomprises the "The coil 5 of the'o'scillatory circuit is, furthermore,

inductively coupled with coil 8 in the anode circuit of the tube, to provide a feed back oscillation system. The intermediate frequency amplifier 11 may include additional filters for preventing the passage of undesired frequencies differing from the intermediate frequency elected for the particular receiver and to make the amplifier sharply selective to a predetermined frequency and prevent any interference caused by interfering receiving frequencies in combination with any one of the available local frequencies. The further elements. shown, such as the detector 12, audio frequency amplifier 13 and loud speaker 14, are similartofthose commonly used in such circuits and mentioned in connection with Figure 1.

Referring to Figure 3, this shows a similar circuit to Figure 3, the only difference being in that a capacitative coupling between the antenna circuit and the oscillatory or input circuit has been provided for by means of a coupling condenser 16. Furthermoreya capacitative inductive feed back is shown in this circuit by means of an additional condenser l7, arranged as shown in accordance v V w 7 'withthe well known practice. stance,'wi1l suffice for producing an intermediate Referring to'Figurel, this illustrates a direct coupling of the antenna circuit in the oscillatory or input circuit, by means of resistance 18.

The particularkind of coupling, however, of antenna circuit with the oscillatory or input circuit is not essential as to the operation'of the receiver, in accordance with the invention and the high-frequency amplifier may, for instance, be interposedbetweenthe antenna and the oscillatory orinput circuit 5, 6; a

I wish it to be'understood'that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications willo'ccur to a person skilled in the art.

What I' claim' is:

1. In a super-heterodyne receiver for short electric waves, comprising in combination a tunable receptor circuit for receiving'incoming oscillations, a vacuum tube having anode, cathode and control electrodes, said receptor circuit being connected to the control electrode of said vacuum tube," feed back connections from the anode circuit of *saidfvalcuumtube' to said input circuit forproducing a local oscillation said circuit having a frequency response curve broad enough to encompass the frequency of said incoming oscillations andj means to utilize adefinite intermediate frequency produced by superimposition ofs aidreceiving oscillation and of said local oscillation. l j

2."In a super-heterodyn'e receiver for short electric waves, comprising'in combination a tunablefreceptoncircuitfor receiving an incoming wave, a vacuum tube having anode, cathode and grid electrode, said receptor circuit being connected to the grid and cathode of said vacuum tube, means whereby said vacuum tube oscillates at a definite tuning frequency, said input circuit having a frequency response characteristic broad enough'lto encompass said incoming wave and utilize afixed --intermediate frequency derived from beatsproduced by said incoming wave and said local wave'bf said tube.

' 3. In ajysuper-heterodyne receiver for short electric-waves, 'comprisingin combination an antenna 'circuit for receiving an incoming wave, a tunable input circuit coupled to said antenna circuita vacuum tube having I cathode, anode and grid electrode, said input circuit being connected to the grid and cathode of said vacuum tube, an anode circuit of said vacuum arranged in feed back connection with said input circuit for producing a local Wave of a definite tuning frequency, said input circuit having a frequency response characteristic broad enough to encompass said incoming wave and the local wave, means whereby said vacuum tube acts as a rectifier, a selective intermediate frequency amplifier connected to the output circuit of said vacuum tube for amplifying a fixed intermediate frequency derived from beats of said incoming Wave and said local wave and further means for utilizing and translating said intermediate frequency current supplied by said amplifier.

4. A short Wave radio receiving system comprising in combination a resonant receptor circuit; means'whereby said receptor circuit oscillates for generating local heterodyne oscillations, the frequency response characteristic of said resonant circuit being broad enough to encompass incoming and local heterodyning frequencies for producing a predetermined intermediate beat frequency; and means for selectively amplifying and translating said intermediate frequency.

5. A short wave r ceiving system comprising in combination a vacuum tube heterodyne oscillator; a tunable receptor circuit for receiving in-- coming oscillations and serving simultaneously as resonant oscillating circuit of said vacuum tube oscillator, the frequency response characteristic of said tunable circuit being sufiiciently broad to encompass both incoming oscillation and local oscillation frequencies to derive a predetermined intermediate beat frequenc and means for selectively amplifying and translating said intermediate frequency.

6. A short wave receiving system comprising in combination a tunable receptor circuit; a mixer tube, said receptor circuit being connected to the grid and cathode of said tube to simultaneously serve as oscillating resonant circuit thereof, the

. amplifying and translating said intermediate frequency.

A short wave receiving system comprising in combination a mixer vacuum tube having cathode, anode and at least onecontrol electrode; a tunable receptor circuit for receiving incoming oscillations connected between the cathode and control electrode of said tube; means including feed back connections from the anode circuit of said tube whereby said tunable circuit acts as an oscillator circuit of said mixer, the frequency response characteristic of said tunable circuit being sufficiently broad to encompass both incoming oscillation and local oscillation frequency for deriving a predetermined intermediate beat frequency; and means for selectively amplifying and translating said intermediate frequency.

8. The method of receiving short wave radio signals by means of a common tunable receptor FRITZ GOTTSCHALK. 

